'He was quite short, dressed in an old-fashioned manner, slightly stooped. There was nothing particularly remarkable about his gait, although he can travel quickly and silently when he wishes. It is his face that grabs the attention. Old, but nothing in it weakened or enfeebled. Tell me he is as old as the city and I would believe you. It is the face of generations, paper pale, tired beyond belief, and filled with sadness. See it, and you must keep looking at it. Dottore Marangoni practises hypnotism on his patients sometimes. He believes that the personality of the operator is more important than any technique; that what he does is an imposition of his will on the subject. That is what I felt like: that this man was trying to take over my mind.'

I let his words evaporate in the night air for a while as I considered whether Cort was being melodramatic, deliberately trying to create some sort of impression for his own ends. Certainly my inclination was to believe that I was hearing a manifestation of the breakdown that Longman considered imminent. But I was aware of my own vision shortly after I arrived in the city; of the old man and the serenade. That, also, had wrought a strange effect on me. Either we were both mad, or neither of us was, and I held firm to a belief in my own sanity.

'That seems a grand claim to make on the basis of two momentary encounters, when you didn't even speak,' I said in a reasonable tone.

'They weren't the only ones,' he answered, anxious to allay my suspicions. 'Over the next few weeks I saw him more and more often. He is following me. Everywhere I go.'

His voice was becoming more high-pitched and hysterical, so I endeavoured to calm him.

'He offers you no injury? Does not threaten you? From your description he could do no harm even if he wanted.'

'No. In that respect he does me no harm.'

'Has he ever spoken to you?'

'Once. Once only. I saw him in a crowd last week as I was walking home from work. He was coming towards me and nodded in greeting as I approached. I could take it no more, so I tried to grab him by the arm to stop him. But I could not. I reached out for his arm, but it was as though it wasn't there. Almost as if my hand passed right through him. He kept on walking, and I called out to him, "Who are you?"

'He stopped, and turned round, and answered in English, as I had spoken to him. "I am Venice," he said. That was all. Then he hurried off again and in a few seconds was lost to sight.'

'He was Italian?'

'He spoke in Venetian. But you see? He is following me, for some purpose of his own. Why else would he say such a thing? Who can he be? Why is he doing this to me? I feel I am going mad, Mr Stone.'

The panic was back, rising higher in his voice. I gripped his arm tightly, trying to inflict pain on him to bring him back to his senses before he lost control. I dared not say that I considered it more likely that this encounter was yet another hallucination, that he should seek medical advice before it turned into a full hysteria. But neither did I mention my own vision; I do not know why. I think that I was slightly revolted by his show of weakness. I saw myself as a man of strength and rationality, and wished to keep my distance.

'Calm, my friend, calm,' I said gently, still gripping tightly. Slowly he relaxed, and obeyed. Then I realised he was shaking with sobs, as his efforts at self-control, at manly dignity, crumbled. I could say nothing; I was deeply embarrassed by the spectacle. It was undignified, we were in a public place and I hardly knew the man. My better self said that Cort must be in dreadful straits to so unburden himself to me; the rest of me wished fervently he had not.

'I am most dreadfully sorry,' he said eventually when he regained control of himself. 'This has been a nightmare, and I do not know where to turn.'

'And what does your wife think?'

'Oh, I don't want to bother Louise,' he said hesitantly. 'Poor thing, she has so much to concern herself with, what with Henry being so small. Besides . . .'

He didn't finish, but lapsed into a moody silence instead.

'Forgive me for asking,' I said as delicately as I could. 'But are you certain this man is real?'

'You think I am imagining it?' He was not angry at my question. 'Believe me, I have considered it. Am I going mad? Is this man a figment of my imagination? Of course, I wonder. I almost hope he is; then at least I could go to Marangoni and he could do . . . whatever such people do with the insane. But his feet make a distinct sound on the pavements. He speaks and smiles. He smells, a very distinct smell, like an old cupboard that hasn't been opened for years, slightly damp, musty.'

'But you failed to touch him, you said.'

He nodded. 'But I felt his breath on me as he spoke. He was as real to me as you are now.'

He gripped my arm as if to reassure himself on that point.

'I do not know what to say,' I answered. 'If this man exists, we must accost him and make him answer questions. If not . . .'

'Then I am insane.'

'There you go beyond my knowledge. I am a practical man. I will assume for the time being that you are not about to foam at the mouth.'

He laughed for the first time since dinner. 'That is good of you,' he said. 'And can I rely on you . . .'

'Not to say a word to anyone? I give you my word. I assume you have said nothing of this to anyone else?'

'Who could I tell?'

We had reached his lodging, a grim, tumbledown place in what I later learned had been the Ghetto, where the Jews of Venice had been corralled by the city until Napoleon liberated them. Whatever good that new freedom might have done the Jews, it had little benefited that part of town, which was as malodorous and depressing as any grim industrial town of England. Worse, I should say, for the buildings were rank and collapsing, a positive rabbit warren of tiny little rooms where once thousands had been crammed in, exposed to every unhealthy miasma that huge numbers and unsanitary conditions might create. Cort lived here because it was cheap; I could well imagine it. I would have insisted on hefty payment even to enter his building. It seems that his uncle (though dutiful in the matter of his upbringing and training) was known for a certain parsimony that came from the belief that pleasure was offensive to God. Cort was therefore kept on a tight leash, and had barely enough to house his family as well as live and eat, although their conditions were poor. His lodging was a necessary economy to put aside some small surplus for diversion.

He saw my look as we stopped by his doorway. 'I do not live in luxury,' he said apologetically. 'But my neighbours are good people, and even poorer than I. In contrast to them I am nobilissimi.'

It would not have served me. But his remarks reminded me that I had engaged to visit Longman's Marchesa. I asked Cort about her. 'A charming woman,' he said. 'By all means go; she is worth meeting. Louise knows her and speaks highly of her; they have become quite close.'

He gave me the address and then shook my hand. 'My apologies for the display, and my thanks for the company,' he said.

I told him to think nothing of it, and turned to walk back to the hotel. Cort and his troubles were wafted away on the night air almost before he was out of sight.